Apparatus for vibrating metals during casting



April 1947- J. F. SCHRUMN 2,419,373

APPARATUS FOR VIBRATING METALS DURING CASTING Filed Sept. 10, 1943 Patented Apr. 22, 1947 APPARATUS FOR VIBRATING METALS DURING CASTING J ewett F. Schrumn, West Newton, Mass., asslgnor to Metals 8.: Controls Corporation, Attleboro, Mass, a corporation of Massachusetts Application September 10, 1943, Serial No. 501,752

2 Claims.

This invention relates to a method of and apparatus for forming metals and alloys.

Among the several objects of the invention may be noted the provision of a method of and apparatus for molding metals and alloys, in which new internal structure is obtained in the metal; the provision of such a method and apparatus in which a substantial grain refinement may be obtained as a molten metal or alloy solidifies; and the provision of such a method and apparatus which is economical and feasible in the use of equipment and operating power. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, steps and sequence of steps, features of construction and manipulation, and arrangements of parts which will be exemplified in the structures and methods hereinafter described, and the scope of the application of which will be indicated in the following claims,

In the accompanying drawings, in which is illustrated one of various possible embodiments of the invention,

Fig. l is a diagrammatic perspective view showing suitable apparatus for carrying out my process; I

Fig. 2 is a copy of a photomicrogr'aph at 30 diameters of commercial zinc cast with treatment by my process and apparatus; and

Fig. 3 isla copy of a photomicrograph of 30 diameters of commercial zinc cast without treatment by my apparatus and process.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

I have observed that cast metals may during solidification inhibit the growth of large crystals ii the metals during solidification are mechanically vibrated at high frequencies in the range of from nine to sixteen kilocycles per second, preferably nine to eleven kilocycles per second. I have also observed that alloying processes function differently if solidification occurs under such vibration, to the extent that new alloy characteristics are produced. Some alloys are brittle because of the formation of embrittling metal components. By means of the invention, these may be controlled through control of the crystal sizes formed during solidification. Also, compression molded powdered metals may have their structure made more homogeneous by vibrating them at said frequencies during molding.

Heretoiore, attempts have been made, in the case of cast metals and alloys, to introduce the high-frequency vibrations in the crucibles in which the metals were melted. Since most; practical crucibles are made of ceramic material and such does not conduct vibrations very well, little progress was made on the subject. In any event, vibrating a hot crucible involves complex equipment and large loss of power, and furthermore the frequencyin that case is not applied during the solidificatiton process, which is important, as will appear. In the case of powdered metal, high-frequency vibration during compression molding has not even been proposed because these are not subject to any melting operation in the process of solidifying compression.

I have found that the various desired effects are obtained if the high-frequency vibrations are introduced during the molding process, instead of the melting process, and particularly during the time that solidification occurs in the case of liquid metals and alloys, or during fina1 compression in the case of compression molded powdered materials. In addition, I have found that a great savmg of power can be effected by vibrating less than the entire mold during the solidification process.

Referring now more particularly to Fig. 1, there is shown at numeral I a metal mold consisting of two separable parts 3 and 5 which between them produce the matrix or mold cavity 7. For simplicity this cavity is shown as a cylinder for the purpose of casting a cylindric slug about 1% inches long and {r3- inch in diameter. The cavity is open at its upper end as indicated at numera} 9 for inpouring of metal. The sections 3 and 5 are held together for casting purposes by clamping means 2 consisting of U-connected side members II with claws l2, a cross bar II under the claws i2, and a clamp screw it. By assembling the mold as shown in the drawing and tightening up'the screw IS, the mold and parts are held assembled. By loosening the screw IS, the part II and it may be separated to allow separation of the matrix-forming elements 3 and't. y

In the bottom of the cylinder 9 and closing its lower end is introduced a solenoid core I! which has a close enough fit in the cylindric opening 9 to seal against any substantial leakage of metal poured into the matrix I, but with enough clearance to allow freevibratory movement of the core l9. For-example, machining.

parts 3, 5 and is with a clearance of about .008" on the 5-inch diameter is satisfactory.

The core I! is mounted in the vibration generating apparatus 2| for imparting longitudinal vibrations to the metal in the mold. Suitable apparatus for this purpose is a magnetostriction oscillator of the type shown for example in the Electrical Engineers Handbook of Fender and McIlwain, third edition, section 7, page 128, Fig. 13. (Volume on Communication-Electronics.)

The vibrations are transmitted to the material in the mold but not substantially to the mold.

The armature rod I! should exhibit magnetostriction characteristics and thus should be composed of the usual alloys for this purpose of iron, nickel, chromium, etc. For example, an alloy having 8 to chromium, 36 to 38% nickel and the remainder iron with 1% or so of manganese to facilitate. forging, has been found suitable (see Pender Mcllwain, supra).

Only diagrammatic magneto coils 23 of the magnetostriction oscillator have been shown herein because the remainder of the oscillator circuit is known.

Briefly, the rod I9 is magnetically polarized and clamped at a node. It is then placed in the coils 23 carrying alternating current at the desired frequency. This causes the rod I! to vibrate longitudinally at the frequency of the alternating current. It is desirable to arrange the mechanical form of the rods so that the desired frequency is the resonant frequency of the rod mechanically, in which case the amplitude of the effect will be large even for very small currents in the coil 23.

Other forms of magnetostrictlon generators for generation of relatively high frequencies may be found at pages 6-11 of Ultrasonics, by Bermann and Hatfield, 1938 (John Wiley 8: Sons, New York).

Operation is carried out by mounting the mold i on a suitable fixed support with the core is in position as shown and the rod 2| in position as shown. Hence the core completes the matrix of the mold. The rod 2| is then vibrated, say at eleven kilocycles (11,000 cycles per second) which vibrates the core I9. Since the core IS in the bottom of the mold fits closely enough to prevent metal from leaking by, but loosely enough to transmit vibration, the end of the core within the mold is vibrating at the above frequency. This arrangement removes the necessity of vibrating the relatively larger mass of the mold, thereby minimizing the vibratin mass which would otherwise be necessary and which is difficult to obtain from reasonably simple magnetostriction generators.

The molten metal, which has been heated elsewhere, such as in an electric furnace, is poured into the mold I in which is the vibrating core II. The metal is allowed to cool and solidify as the vibrations are transmitted thereto.

After the slug 2! has cooled off, the vibration of rod 2| may be ended, the screw II loosened and the clamp removed, whereupon separation of the mold parts I and {will result in falling out of the sl Typical results may be noted in connection with the pouring of a slug of zinc as indicated at numeral 25. In Fig, 2 is shown a photomicrograph of a sample of zinc which was poured into the mold I and solidified under vibrations 0! 11,000 kilccycles per second from the rod 2|; and in Fig. 3 is shown a photomicrograph from the same sample of zinc when poured into the mold and solidified without vibration. The great improvement in fineness of grain is at once apparent in Fig. 2, as compared to Fig. 8.

By pouring alloys into the mold under high frequencies introduced from rod 2|, variations are also obtained in alloying characteristics of alloy components poured therein.

Also, compression molding of powdered metals may be effected by compressing these in a cham. ber having inserted therein high-frequency vibrating plug. This hasthe effect of orienting the articles of powdered metal more closely as they are brought into a state of iinal compression.

It will be seen, in view of this invention, that it is not necessary in order to obtain the benefits of high-frequency vibrations in molding processes to vibrate the whole mold. If it were necessary to vibrate the whole mold, the process would become impractical to carry out in connection with molds of any substantialsize. However, by introducing the vibrator into an open part of the mold and transmitting vibrations to the contained material in themo'ld without vibrating the mold as a whol the useful effects are obtained without the expenditure or unnecessary amounts of energy. and withoutintroducing com- The vibrations which plexities of structure. bring about the desired orientation in structure toarrange .a mold of any shape so that some part is used as a driver in a manner similar to nection with the vibrating core I.

The term high-frequency is to be interpreted herein as frequencies within the higher ranges audible to the human ear, for example nine to sixteen kilocycles.

It is to be understood that other means may be used for obtaining the vibrations but the chief advantage of magnetostriction generators lies in the simplicity and cheapness of their construction.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A mold comprising separable matrix elements, means-for holding said elements together to form a cavity, said elements being formed to provide a cylindric opening joining the cavity with the exterior, a cylindric plug movably sealed that described in ot'min said opening to prevent leakage, and means for applying high-frequency vibrations to said plug, the end of the plug being exposed to contact by the material which is formed in the mold.

2. 'A mold comprising separable matrix elements, means for holding said elements together to form a. cavity, said elements being formed to provide an aperture joining the cavity with the exterior, a solenoid core movably sealed in said aperture to prevent leakage from said cavity, and means for applying high frequency vibrations to said solenoid core, the end of said solenoid core being exposed to contact by the material which is formed in the mold. v

JEWE'IT F. SCHRUMN.

REFERENCES CITED The following references are of record in the file of this patent:

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